Boris Johnson has refused to face an investigation into a controversial deal between City Hall and Chinese developers.
Johnson had been called to appear before two London Assembly committees to discuss the deal with the firm ABP.
However, he has refused to co-operate, saying that it would not be "appropriate" for him to face further questions from them on the deal.
The Assembly launched their investigations last month following allegations by Channel Four News that an adviser to ABP had donated large sums to the Conservative party in advance of the £1 billion deal to develop Royal Albert Dock.
Companies House records confirm that Anglo-Chinese businesswoman Xuelin Black set up a company called London China ABP in 2008. She later donated over £160,000 to the Tories in advance of the Albert Dock deal according to the electoral commission.
Black, who is now married to Conservative home office minister Lord Bates, has been photographed with several leading Conservative politicians including David Cameron and Johnson himself. However, she insists she was not paid by ABP and did not make the donations on their behalf.
Following Channel Four's broadcast, Johnson faced allegations that the mayor's investment quango London and Partners L&P had shared an office with the developers.
He admitted to the London Assembly this was the case but insisted that there was nothing untoward about this. He was also asked about further claims that a GLA official involved in the tendering process had since moved over to work for ABP. Johnson acknowledged that the officer Tom Keady, had started working for ABP six months after leaving City Hall.
Channel Four also broadcast allegations about the company's human rights record in China. Johnson told the Assembly he had seen no evidence to support these claims.
Following the meeting, the London Assembly passed a motion calling on the mayor to appear before City Hall's audit committee and a joint session of the Economy and Planning Committees to discuss the deal in more detail.
However Johnson has refused to appear at either claiming that it would not be "appropriate" to answer further questions in front of the committee.
"You have asked for a commitment from me that I will appear before the audit panel and the economy and planning committees to contribute to their scrutiny sessions on this topic," he wrote in a letter to the Assembly.
"I will of course ensure that as many of my advisers attend as you require along with the lead GLA officials. I do not think it would be appropriate or necessary for me to attend in the first instance."
He added that he would only answer questions on the deal once they had finished their inquiries.
Johnson is now facing calls for a full independent investigation into the matter.
"It is totally outrageous that the mayor is refusing to be held accountable for his decisions on the Royal Albert Dock. He was the one who signed off the deal, yet he thinks it's alright to refuse to answer questions on the subject," London Assembly Labour group leader Len Duvall AM said.
"Londoners need to know that Boris' big international deals are getting best value for the capital. The mayor's refusal to open up the process to proper scrutiny will just fuel concerns about this development, as it stands the way this deal was done is as transparent as mud…
"That is why we desperately need an independent investigation to remove the politics from this and get to the bottom of the legitimate questions raised about the deal."
A spokesperson for the mayor declined to comment.